The world production of cellulose and lignin on land is 60 billion ton per year and the stock of cellulose and lignin is 1 000 billion ton.
The world consumption of fossil fuels is 8 billion ton per year.
The food production in the world is 3 billion ton per year.
From these 3 numbers we conclude that, to take out from food, materials to produce bio ethanol or vegetable oils for biodiesel would not solve the problem of substituting fossil fuels, and would cause hunger.
On the other side, there are large surfaces of arable land, which are not cultivated or which produce plants not suitable for food. In these surfaces, the production of cellulose and lignin from trees or bush is possible. On the other side, cellulose and lignin contained in biomass is a side product of many food crops.
One of the crops which produce large quantities of cellulose and lignin per hectar and per year is sugar cane, which has an yield of 80 ton per hectar.
In one ton of sugar cane there are about 80 kg of sugar, which may be converted to 40 kg of bioethanol. Besides sugar there are 250 kg of cellulose and hemicellulose and 120 kg of lignin, which is presently not converted to liquid fuels.
The substitution of fossil fuels is also an important motivation to improve the process for producing biofuels, because of the carbon dioxide which they produce by burning. Although cellulose and lignin also produce carbon dioxide by burning, the same quantity of carbon dioxide was previously taken out of the atmosphere by photosynthesis to produce cellulose and lignin.
As a consequence, to convert cellulose and lignin into a liquid fuel is since decades a challenge for scientists, because the existing cars and trucks could drive with such a liquid biofuel without major changes in the motor.
The exhausting oil reserves and the political dependence on unstable countries producing oil is also a major problem today, which motivates the research of renewable alternatives.
In the literature as attach, there are research works on following reaction steps: